Control for air cooled condensers



N0 18, 1969 s. J. KGCHER ETAL v`v"33473533 CQNTROL Fon AIR COOLED CONDENSERS Filed larch s. 1968 Unted States Patent O U.S. Cl. 62-196 1 Claim ABSTRACT OF THE DISCLOSURE An automatically operable all-weather control for refrigeration systems embodying an outside condenser which is exposed to changes in atmospheric temperature and especially winter conditions.

BACKGROUND In the refrigeration and air conditioning field, it has become common practice to use air-cooled condensing equipment instead of water-cooled systems. While these air-cooled systems have become exceedingly popular, they do present a problem `with respect to the control of head pressure during low temperature ambient air operation.

For example, head pressure of air-cooled units is directly responsive to the temperature of ambient air, and while head pressure is high in warm weather, itis very low in cold Weather. Thus, as the ambient air temperature drops across the condenser, the pressure drops in the entire high side ofthe system, and the expansion valve feeds less and less refrigerant to the evaporator until nally no refrigeration takes place due to the lack of pressure differential across the expansion valve.

In efforts to control this problem, several methods have heretofore been adopted. One of the more widely used is a modulated bypass System which employs a control valve for holding back the discharge pressure causing it to ow through a pressure-actuated modulating valve to give instant pressure in the receiver. As the discharge pressure builds up to the setting of the control valve, excess liquid travels to the condenser and builds up pressure in the condenser to keep the system running. In another winterizing arrangement, 'a constant pressure regulating valve is installed in the condenser return, and as the ambient air temperature drops and the discharge temperature falls below the setting of the valve, it closes to thereby restrict refrigerant flow from the condenser. Another system employs a pressure regulating valve between the compressor and condenser, a reverse acting regulating valve in the bypass between the compressor discharge and the condenser return, and a check valve between the condenser and the bypass for preventing pressure from returning to the condenser up the return line.

Other winterizing systems use an electrically heated receiver mounted above the condenser so that there is always warm liquid present of sufficient pressure to feed the evaporator, the valving and piping arrangement being such that hot gas is pushed into the lled condenser forcing cool liquid into the receiver under pressure for mixing with the heated liquid which is then fed to the evaporator.

All of the systems hereinabove described utilize the principle of flooding the condenser to limit its etiiciency for low ambient temperature operation. However, the use of modulating arrangements in an eiiort to control head pressure during operation fails to give proper control when the unit is shut down, resulting in various startup difficulties due to crankcase foaming, short cycling and the like. Also, experience has shown rather prevalent valve leakage as well as undesirable equipment requirements. Furthermore, with an elevated receiver, condenser capacities are oftentimes considerably less than the rated capacity due to the backup of liquid, and generally speaking, the prior systems have required relatively complicated and unreliable equipment.

SUMMARY An object of the present invention is to provide an improved refrigeration system employing an air-cooled condenser and adapted for eicient year-around operation in all types of weather and which obviates the aforesaid disadvantages and objections.

Another object of this invention is to provide an improved refrigeration or air conditioning system embodying an air-cooled or evaporative condenser and in which a heated receiver is mounted below the condenser to permit free drainage of the condenser during summer months when full condenser capacity is essential.

A further object of the invention is to provide an improved refrigeration system which utilizes an air-cooled condenser and which has provision for the maintenance of high side pressure during shutdown, whereby liquid is forced from the receiver up into the condenser to ll the same.

Still another object of the present invention is to provide a refrigeration or air conditioning system employing an air-cooled condenser with improved Vautomatically operable means for maintaining adequate receiver pressure at all times, regardless of the -ambient temperature, to feed the evaporators -while restricting the ow of liquid from the condenser until the pressure in the condenser reaches that of the receiver, thus providing for normal operating conditions.

These and other objects and advantages of the invention Iwill become apparent from the following detailed description.

THE DRAWINGS A clear conception of the construction and mode of operation of a typical refrigeration system embodying the present invention will be had by referring to the drawing accompanying and forming a -part of this specification wherein like reference characters are used to identify the same or similar parts.

FIGURE l is a diagrammatic view illustrating a typical refrigeration system having an air-cooled condenser and embodying the present improvements;

FIGURE. 2 is an enlarged vertical section through a typical back pressure regulating valve employed in the system; and

FIGURE 3 is a similarly enlarged vertical section through a typical spring loaded check valve as also used in the system.

DETAILED DESCRIPTION Referring to the drawing, the lsystem illustrated therein comprises, in general, a compressor 6, an air-cooled condenser 8, a receiver 10, and an evaporator or cooling coil 12. The condenser 8 is connected with the high pressure discharge side of the compressor 6 by a refrigerant supply line 14, and the cooling coil 12 communicates Aat its inlet end with the receiver 10 via conduit 16 and at its outlet end with the low pressure inlet side of the compressor via conduit 18.

The compressor 6 is of any suitable type Vadapted to receive spent gaseous refrigerant from the cooling coils 12 through the suction line 18 and to compress and deliver the same under high pressure through the supply line 14 to the condenser 8. A thermostatically controlled expansion valve Z2 at the inlet end of the cooling coil or evaporator 12 controls the operation of the compressor 6 according to demand. The condenser 8 is of the aircooled or evaporative type located exteriorly of the wall 24 so as to be exposed to the ambient atmosphere, and the capacity of the condenser 8 is therefore variable dependent upon weather conditions. In the embodiment shown, the compressor 6 and receiver 10 are also located outside, but they may be located interiorly if desired. A one-way check valve 26 is interposed in the high pressure discharge line 14 to prevent backup, and the condenser 8 and evaporator 12 may be provided with the usual refrigerant ow control valves, not shown.

In accordance with the present invention, the receiver 10 is mounted below the condenser 8, and the condenser is accordingly free-draining during the summer months when full condenser capacity is a requirement. Also, the receiver 10 is heated externally by a suitable heater 30 which may, in practice, be in the nature of a heating blanket controlled by a thermostat 32 extending into the receiver. The thermostat 32 is adjustable and can be set for the proper temperature to maintain sucient high side pressure during shutdown to force the liquid from the receiver 10 up into the condenser 8 by way of a conduit 34 and thereby ll the condenser. Mounted on the receiver 10 is a suitable float-actuated liquid level gauge 36 for indicating the level of refrigerant in the receiver, and initially the receiver should be charged to `approximately one-half full with a suflicient amount of liquid being maintained therein at all times to submerge the bottom of the line 34 in order to permit liquid to be forced into the condenser 8 while also providing an adequate liquid supply in the receiver under high pressure conditions for quick response on start-up.

Interposed in the high pressure line between the compressor 6 and the condenser 8 beyond the check valve 26 is back pressure regulating valve 40 which may be of any suitable commercially available type such as that shown, for example, in FIGURE 2. The valve 40 is adjustable, and when the System starts up, this main regulating valve 40 remains closed until the pressure reaches the set pressure of the valve whereupon the valve will open and permit high pressure gas to be forced into the condenser. The receiver 10 is also placed in communication with the high pressure line 14 between the check valve 26 and pressure regulating valve 40 by means of a conduit 42, and a spring loaded check valve 44 is interposed in this conduit. The spring loaded check valve 44 may likewise be of any suitable type such as that `shown in detail in FIG- URE 3 which is also commercially available. The receiver 10 may also be provided with a safety valve 46 and a purge valve 48 in accordance with customary practice.

Referring to FIGURE 2, the pressure regulating valve shown therein by way of example comprises a valve body or housing 52 coupled to the line 14 by threaded coupling members 54, S6 and having inlet and discharge ports 58, 60, respectively, with a valve seat therebetween. The body 52 contains a main valve disc 62 constantly urged toward seated position by ya spring 64 and guided in its movement on a stern 66. A valve bonnet 68 is secured to the body 52 and contains a chamber 70 housing a spring 72 reacting against the top of a diaphragm 74 spanning the lower end of chamber 70, the compression of the spring being adjustable by a stem 76 threaded in the bonnet 68. The bottom face of the diaphragm 74, in turn, is exposed to the inlet pressure port 58 by way of a restricted passage 78, and the diaphragm 74 is normally seated against a pilot assembly 80 by the action of the 4spring 72 until there is a suicient build-up of pressure below the diaphragm to overcome the spring 72. A power piston 82 is positioned for sliding movement below the' pilot assembly 80 and carries a valve actuating stem 84.

In operation, the back pressure regulator 40 is closed with the valve disc 62 seated as shown until the pressure in line 14 and inlet 58 exceeds preset pressure as determined by the adjustment of the stem 76. Pressure in the inlet 58 is communicated to the lower `side of the .4 diaphragm 74, and as the pressure rises, the diaphragm exerts force upwardly against the diaphragm spring 72. When the pressure rises suiciently above the preset pressure, the diaphragm is lifted from its seat on the pilot permitting pressure from the chamber below the diaphragm to enter behind or on top of the power pist0n 82. When the pressure acting on the power piston exceeds the pressure existing in the port 60 by a predetermined amount, the piston 82 is moved downwardly against the `action of the spring 64, thereby gradually unseating the main valve 62 and opening the inlet 58 to the outlet port 60. Whenever the pressure existing in line 14 and inlet 58 drops below the preset pressure, the diaphragm 74 again moves downwardly to close the pilot seat. Then, as pressure above the piston 82 escapes through a small bleed port 86 to the port 60 on the downstream side of the regulator, the valve closing spring 64 gradually returns the valve disc 62 to closed position thus preventing refrigerant flow through the regulator and consequently causing the pressure in line 14 to remain up to the adjusted setting.

Referring now to FIGURE 3, the spring loaded check valve shown therein by way of illustration comprises generally, a valve body 90 secured in the line 42 as by means of coupling members 92, 94 and provided with inlet and outlet ports 96, 98, respectively, with a valve seat therebetween. The valve body 90 has a bore 100 opening toward the valve seat, and a piston 102 is contained for sliding movement within this bore. The piston 102 is constantly urged toward the valve seat by a spring 104 confined between the top or back side of the piston and a cap or cover 106 closing the upper end of the bore. The piston valve 102 is accordingly maintained closed by action of the spring 104 which may be selected to exert a predetermined closing pressure, and when the pressure in the inlet 96 is sufficient to overcome the spring action, the valve 'piston 102 is raised from its seat and flow is permitted through the valve to the discharge port 98. When the upstream and downstream pressures are equalized, the weight of the piston and action of the spring 104 will force the piston valve 102 against its seat and thereby stop further uid ow through the valve.

During low temperature conditions, the condenser 8 tends to condense the gas rapidly and thereby reduce the pressure in the condenser to a point below the inlet pressure setting of the control valve 40. When the pressure in the condenser 8 and the receiver 10 is reduced to a point below the setting of the spring loaded check valve 44, this check valve will open and force discharge gas directly into the receiver 10. This maintains adequate receiver pressure at all times sucient to feed the evaporator or cooling coil 12 and the pressure in the receiver 10 restricts the ow of liquid out of the condenser 8 until the liquid has backed up in the condenser to a point wherein the condenser pressure matches the receiver pressure. There will then be a flow of gas into the condenser 8 and a tlow of liquid out of the condenser at a rate suicient to match the load requirements. Once the main valve 40 has been preset and the thermostat 32 controlling the heater 30 has been preset, the system will function automatically year around regardless of weather conditions. There is positive start-up of the system due to the pressure maintained by the heater 30 during compressor shutdown, and to provide for immediate start-up of the compressor 6 especially with the compressor located outside, it too may be provided with a thermostatically controlled heater 50 in the crankcase.

I n actual tests, the control system has proven highly successful and has performed satisfactorily in ambient conditions of 20 F. and lower. While the invention has been illustrated and described as being incorporated in a system having a single evaporating or cooling coil adapted for use either for ordinary refrigeration or air conditioning purposes, it is not intended or desired to limit the system by reason of such specific disclosure. It is also contemplated that specific descriptive terms used herein shall be given the broadest interpretation consistent with the disclosure and other types of commercially available pressure regulating valves and spring loaded check valves may be used in place of those specifically shown in FIGURES 2 and 3.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. In a refrigeration system including a refrigerant compressor for supplying refrigerant under pressure through a supply line to the inlet of an atmospheric temperature responsive condenser, a liquid refrigerant receiver, and an evaporator connected at its inlet end with the receiver below the level of the liquid therein and connected at its outlet end with the low pressure side of the compressor; a conduit communicating said receiver with the condenser, conduit means including a spring loaded check valve for connecting the receiver with the high pressure refrigerant supply line for pressurizing said receiver to force refrigerant liquid from said receiver into said condenser through said conduit and thermostatic means for heating the receiver to maintain a predetermined temperature therein.

Referencesv Cited UNITED STATES PATENTS 3,324,673 6/ 1967 Lindahl. 3,031,859 5/1962 Mann. 3,389,576 6/1968 Mauer 62-196 MEYER PERLIN, Primary Examiner 

